Ahiyapur police in Muzaffarpur arrested one Vijay Kumar Gupta in connection with the mysterious death of junior engineer Sarita Kumari on Monday.

Sarita (35) was posted in the district's Muraul block to oversee works carried out under Mahatma Gandhi National Rural Employment Guarantee Act.

The deceased engineer's skeleton, a pair of slippers, clothes and a burnt chair were seized from an under construction house in Kolhua Bajrangbali Vihar Colony in Muzaffarpur town, around 80km north of Patna, on Monday.

A jerry can with kerosene was also found on the spot.

Muzaffarpur senior superintendent of police (SSP) Vivek Kumar said on Tuesday the case was being probed from both murder and suicide angles. "The owner of the under construction house, Vijay Kumar Gupta, was picked up after the deceased's husband, Vijay Kumar Naik, accused him of killing his wife."

"The police have recorded the statement of the victim's husband. Efforts are on to ascertain the reason behind the incident," the SSP said, adding that two letters purportedly written by Sarita had been seized from the house.

"One of the letters addressed to her mother was recovered yesterday (Monday). The second letter was recovered from a nearby house today (Tuesday)," the SSP said.

The SSP said though Sarita owned a three-storeyed house in the same locality, she had taken Gupta's building on rent for her official work. She used to meet people in the underconstruction house, he added.

The letters suggested that Gupta, who was associated with her for the past six years, harassed the junior engineer. They also revealed some differences had cropped up between the two over transaction of money.

Sarita's relationship with her husband soured because of Gupta. "Her husband had not visited her for the past seven months," an investigating officer told The Telegraph.

While Naik used to stay at his ancestral village, Fulkahan, in Sitamarhi district, Sarita was living in Muzaffarpur with her minor son Aryan, a student in a local school. Sarita's elder son, Dhruv Kumar, studies in a government polytechnic college in Darbhanga.

The incident came to the fore when Gupta opened the door of Sarita's room on Monday evening. He raised an alarm and also informed the police, who arrived only to find skeleton and ashes all around. A forensic team later visited the spot and collected samples.

Sarita's younger son, Aryan, was not present in the house at the time of the incident. A neighbour told the police that Sarita was last seen around 7pm on Monday.

The station house officer of Ahiyapur police station, Anil Yadav, said the identity of the deceased was ascertained from clothes and slippers found at the spot. "The slippers and clothes belonged to Sarita," the SHO quoted Sarita's mother Kusum Devi as saying.

He said the letters would be sent to handwriting experts at the state forensic science laboratory in Patna.

Aryan told the police that he had talked to his mother on phone around 7.30pm on Monday and she had behaved as usual. "I didn't feel anything unusual. Mother appeared normal. "

Sarita had never complained to the police against her husband though the couple lived separately, the SHO said, before adding that Gupta's relationship with Sarita had primarily become the bone of contention between the two families.

Sarita's husband Naik is unemployed.